1. Field of the Invention
This invention relates to a projection display apparatus and a projection display system in which data is furnished from outside and light is projected to display an image.
2. Description of Related Art
There is such a display system in which a liquid crystal projector is controlled by a personal computer as a control device for making presentation. In such display system, the projector is controlled by the personal computer to project an image on the screen.
When a pointer position displayed along with an image using this display system is moved to make presentation, a projector and a remote controller making infrared communication are frequently used. That is, the remote controller is actuated by a user to generate an actuating input signal to output the signal as the IR light to an IR light receiving portion of the projector. This causes the projector to output an actuating input signal over a dedicated cable to the personal computer to move the pointer position responsive to the user actuation for display.
In the above-described display system, the personal computer and the projector are interconnected over a projector control cable for controlling the projector, a pointer dedicated cable for controlling the pointer by a remote controller annexed to the projector, and over an RGB cable used for transmitting RGB picture data from the personal computer to the projector.
For controlling the projector, the projector is controlled by the personal computer by a serial interface such as RS-232C and a projector control cable pursuant to RS-232C. In such display system, a projector control signal for controlling the projector is output from the personal computer over the RS232C cable to the projector.
When displaying a picture on a display screen by projecting the light by the projector, the personal computer inputs a projector control signal to the projector over a projector control cable, whilst picture data to be displayed on the display screen via RGB cable is input to the projector.
If, when a picture is displayed on the display screen, a remote controller or a pointing device of the personal computer is acted on by the user, a pointer controlling signal is input from the personal computer over a pointer dedicated cable, such as PS2 cable, to the projector.
However, in this display system, the interface and the cable used for transmitting e.g., a projector control signal from the personal computer to the projector, as well as the interface and the cable used for controlling the pointer position specified by e.g., the remote controller, are of different standards. So, in the above-mentioned display system, it has been necessary to provide the interface and the cable for transmitting/receiving the control signal etc separately from the interface and the cable for performing pointer control.
In order to overcome such inconvenience, it has been contemplated to provide an interface and the cable for transmitting/receiving the control signal etc and the cable for performing pointer control in common. However, there is a limit in the number of connectors provided in the small-sized portable personal computer, such that the connector is taken up by the projector control cable used for interconnecting the projector and the portable personal computer to render it impossible to make connections to other devices, such as a mouse.
Moreover, if, in making presentation using the above-described display system in e.g., a small conference hall, the pointer control employing a remote controller emitting the IR light is used, the user operation making the presentation tends to be complicated.
In addition, if, in the conventional display system, employing a projector, plural projectors are used, dedicated switchers etc., adapted for coping with e.g., RS 485, need to be used, thus raising the cost. In such conventional system, the circuit load in the projector tends to be increased.